When a woman covers her hair with a shaitle that looks like her own hair, yes, she is technically covering this Erva, BUT, it is exactly the same if a woman covers other parts of her body which are considered Erva with skin colored, tight clothing and a photograph of exactly what is underneath. Yes, she is technically covered…but you can’t really tell.
Okay, going with your example. What is wrong with wearing skin colored clothing? I can think of two issues- 1) it’s provocative 2) maras ayin. Regarding issue #1 if a wig is refined it’s not a problem. Regardng issue #2 as established earlier in this thread, in a place where sheitels are commonplace maras ayin doesn’t apply. And btw- the only time I have ever been unsure whether or not a woman was wearing a sheitel was when she wore it further back blending it in with her own hair. The skin colored part doesn’t fool anyone (unless they’re not used to it)